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Bushings for High Voltage AC Applications

Selection guide

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During selection of bushings for high voltage applications several important factors have

to be considered to ensure that the correct equipment is chosen. This Selection Guidehas been produced to simplify the selection process and to ensure that sufficientinformation exists to allow the correct selection to be made.

The technical information pertaining to bushings manufactured by ABB Components hasbeen divided in separate documents, with one document for each type.

The information provided in this document is intended to be general and does not coverall possible applications. Any specific application not covered should be referred directlyto ABB Components AB, or its authorized representative.

ABB Components AB makes no warranty or representation and assumes no liability forthe accuracy of the information in this document or for the use of such information. Allinformation in this document is subject to change without notice.

ABB Components also manufactures the following products:

On-load tap-changers

Motor-drive mechanisms

The selection process forAC bushings _________________ 3

Input data ___________________ 4Type of application ___________________ 4Electrical requirements ________________ 4Ambient conditions includingmecanical requirements _______________ 4

Selection ____________________ 5

Bushings - product scope _______ 6

Product documentation _________ 8Technical guide ______________________ 8Installation and maintenance guide _______ 8Product informations __________________ 8

Table of contents

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Information about mounting and service is given in theInstallation and Maintenance Guide, available for all types.

For special questions, product informations giving moredetailed information are available upon request. For anyfurther assistance, please do not hesitate to contactABB Components.

Installation andmaintenance guide

General

product informations

ABB Components AB

Sales department

Below is a schematic plan, showing the selection process.

Before the selection can start, a number of different inputdata have to be collected. After that the selection guide canbe used to select the most suitable bushing for theapplication in question. When the type of bushing isidentified, the selection of the right size is made in theapplicable Technical Guide. In the Technical Guide, thespecial features, such as connection details, oil levelindicator, inclination of the bushing etc. are chosen.

The selection process for AC bushings

Selection guide

Selection (p. 5):

Quick reference for transformer bushings

Application

Nominal voltage

Lightning impulse

Switching impulse

AC 1 min. dry

AC 1 min. wet

Phase-to-ground voltage

Current

Creepage distance

Order

Input data

Electrical requirements

Referred standards(IEC 137, ANSI/IEEE, others)

Ambient conditions including mechanicalrequirements

Technical guide

Ratings for all standard sizes of bushings

Dimensions for all standard sizes of bushings

Special options for the bushings

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IEC ANSI

Air temperature 30 C 40 C

Transformer oil temperaturerise above ambient 60 K 55 K

Maximum hot spot inOIP bushings 105 C 105 C

Maximum hot spot inRIP bushings 120 C 120 C

Required power factor if standards other than IEC orANSI are referred toThis is made as a routine test on all bushings. IEC requires

the bushing to have a power factor below 0.7 %. ANSIrequires the bushing to have a power factor below 0.55 %.

Ambient conditions includingmechanical requirements

Referred standardABB Components bushings fulfil the ambient and

mechanical requirements according to IEC (IEC 137).ANSI (IEEE C57.19.01-2000) specify certain dimensionrequirements which deviate from ABB Componentsbushings. Please check in our bushing Technical Guidesor directly with ABB Components for further information. Ifany other standard is required, please contactABB Components.

Required specific creepage distanceIEC defines the specific creepage distance as the totalcreepage distance divided with the rated voltage whereasANSI defines it as the total creepage distance divided bythe line-to-ground voltage. This means that there is aconversion factor of 3 between IEC and ANSI.

IEC defines four different classes depending on the degreeof pollutions in the area where the bushing is intended to

be used:

Class 1 16 mm/kV for lightly polluted atmospheresClass 2: 20 mm/kV for medium polluted atmospheres

Class 3: 25 mm/kV for heavily polluted atmospheresClass 4: 31 mm/kV for very heavily polluted atmospheres

The most common classes are 20 and 25 mm/kV.

Required cantilever loadBoth IEC and ANSI have specified values for the requiredcantilever load. In the new revision of IEC 137 two different

levels for the cantilever load are given: Level 1 for normal

application and Level 2 for special applications with severemechanical loads. Level 1 corresponds to the level in theprevious revision of IEC 137.

Type of application

ABB Components AC bushings are made for five differentapplications:

Air to OilOil to OilOil to SF

6

Air to AirAir to SF

6

For DC application, please contact ABB Components forfurther information.

Electrical requirements

The following electrical data must be known prior tocommencing the selection process:

Referred standardGenerally ABB Components bushings fulfil the electricalrequirements according to IEC (IEC 137) and ANSI (IEEEC57.19.00-1991 and IEEE C57.19.01-2000). If any otherstandard is required, please contact ABB Components.

Rated voltageNormally the phase-to-phase voltage for the system wherethe bushing is intended to be used.

Required lightning impulse levelNormally the same lightning impulse level as for thetransformer. The lightning impulse test is a routine test forbushings with a rated voltage equal to or above 300 kV.

Required switching impulse levelNormally the same switching impulse level as for thetransformer. This is a type test and is made during wetconditions for bushings for outdoor application.

Required test level for the dry 1 minute AC testNormally about 10% above the test level of the induced testfor the transformer. This test is made as a routine test on

all bushings.

Test voltage for the wet 1 minute AC testThis is a type test for bushings with a rated voltage below300 kV.

Phase-to-ground voltageThis is the actual continuous AC voltage that the bushingis subjected to.

Nominal currentThis is the maximum continuous AC current the bushingcan carry at a certain air temperature and a certain oiltemperature with the hot spot of the bushing at maximum

105 C (120 C for RIP). The following temperaturesapplies for IEC and ANSI:

Input data

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Rated Lightning Switching Routine AC 1 min. Phase-to-ground Current Creepagevoltage impulse impulse, wet AC 1 min. wet voltage distance

(kV) (kV) (kV) dry (kV) (kV) (kV) (A) (mm)

Air to Oil:GOB 170 750 N.A. 365 325 170 1250 4800GSA-OA 170 750 N.A. 365 325 100 2000 5504*)GOM 300 1175 850 505 550 200 1600 7550GOE 800 2550 1600 1000 1000 485 5000 20000GOH 36 200 N.A. 80 75 36 25000 760

Oil to Oil:GSA-OO 245 1050 N.A. 505 N.A. 141 2500 N.A.

Oil to SF6:

GOEK 800 2550 N.A. 1000 N.A. 485 5000 N.A.

Air to Air:GOBL 145 650 N.A. 300 275 145 1250 4080GSA-AA 170 550 N.A. 260 230 100 2000 3913*)GOEL 800 2100 1600 1000 1000 485 5000 20000GGAL 550 1675 1300 750 750 485 5000 17500*)

Air to SF6:

GGA 550 1800 1360 800 800 318 4000 13750*)

Maximum ratings for different types of ABB Components bushings. See also quick reference above.*) Silicone rubber sheds.

Selection

Quick reference for transformer bushings.

Rated voltage

Current

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Bushings - p

L 33152 L 36531 L 35702 L 33150 L 37060 L 37062

Type GOB GOM GOE GOH GOEK GOBL

Technical Guide1ZSE 2750-102 1ZSE 2750-108 1ZSE 2750-105 1ZSE 2750-107 1ZSE 2750-106 1ZSE 2750-104

Installation andMaintenance Guide 2750 515-12 2750 515-41 2750 515-1 2750 515-85 2750 515-116 2750 515-117

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oduct scope

L 26836 L 36697

GOEL GGAL GGA GSA-OA GSA-AA GSA-OO

- - 1ZSE 2770-100 1ZSE 2750-111 1ZSE 2750-112 1ZSE 2750-116

2750 515-132 - 2770 501-2 2750 515-115 2750 515-133 2750 515-138

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Technical guide

The Technical guide provides ratings and dimensions forall standard sizes of a particular bushing. Several designoptions are also given.

Colour of air side insulatorBrown and light grey porcelains are available as standardfor most of our bushings with brown as the most commonone.

Silicone rubber sheds are only available in light greyRAL 7035.

Type of connection

Draw lead:This type of connection is the most common onefor low currents. The current is carried by a stranded cablepulled through the bushing. The inner terminal can beconnected to the cable either by brazing or crimping.Guidance for the needed area of the cable is also given inthe Technical Guide.

Solid rod:This type of connection is used when the currentbecomes too large to be carried by a stranded cable. Thecurrent is carried by a solid rod pulled through the bushing.

Draw rod:This type of connection is used for the GOE andGOEK on higher currents to get a simple design of the

transformer together with an easy mounting of the bushingon the transformer. The current is carried by a conductortube, included in the bushing. As the draw rod solutionsimplifies the transformer design it is used quite frequentlyalso at lower currents.

Outer terminal:Aluminium and copper alloy are availableas standard for most of our bushings. Other materials anddimensions are available upon request.

Type of shielding

Shield for the transformer side of the bushing is normallyavailable as standard. Depending on voltage level andtype of bushing the shield is epoxy coated or insulated withpress board. Guidance for the design of the position of thebushing in the transformer is also given in the TechnicalGuide. If other bottom end shields are used, ABBComponents can assist with field calculations to confirmthe compatibility between the bushing, the shield and thetransformer. Type tests as well as routine tests areperformed with our standard shields mounted on thebushings oil side.

Oil level indicatorOil level indicators are normally requested on oil-filledbushings. This is an option for smaller bushings. The

indicator comprises a sight glass or is of a magnetic type,depending on the type of bushing.

Pressure monitoringPressure monitoring equipment is an option on bushingsfor connection between SF

6and the transformer oil. This

gives the advantage of continuous monitoring includingalarm and trip functions.

Installation and maintenance guide

The Installation and maintenance guide providesinformation on how to handle the bushing. Detailedinformation about inner and outer connections andmaintenance are also important parts of this document.Each product type has its own Installation and maintenance

guide.

Product informations

Product informations are available to answer generalquestions that are not covered in the Technical guides orthe Installation and maintenance guides. These questionsinclude the following:

Gasket in ABB oil impregnated bushings(2152 4016-3)Gives a short description about the gasket system used inABB Components' bushings.

Repair of damaged porcelain insulator(2750 514-23)Describes how to repair small damages in porcelains.

Bushing diagnostics and conditioning(2750 515-142)Guidelines for diagnostics and conditioning of bushings.

Bushing oil(2750 515-84) General information about theoil used in ABB Components' bushings.

Seismic calculation on ABB bushings mounted on atransformer tank cover (2750 515-88) Guide how tocalculate seismic withstand on ABB Components' bushings.

Resin impregnated paper bushings (2750 515-130)Comprehensive information about the RIP technologyused in ABB Components' bushings type GSA.

Silicone rubber (2750 515-131) Comprehensiveinformation about the silicone rubber insulators used onABB Components' bushings type GSA.

Difference between RIP and OIP bushings(2750 515-136)Particular features of RIP and OIP bushingsfrom ABB Components.

Product documentation

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Notes:

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Notes:

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1ZS

E

2750-100,Rev.2,Languageen,2000-10-30

ABB Components ABVisiting address:Lyviksvgen 10Postal address:SE-771 80 Ludvika, SWEDENTel.+46 240 78 20 00Fax +46 240 121 57E-mail: sales@se.abb.comwww.abb.com/transmission